Manual 3D digitization, commonly known as Optical Scanning, uses equipment and software including full-spectrum optical metrology, limited spectrum (e.g. Light Emitting Diode), and LASER. Typically, a human either places and positions the part in front of the sensor or moves both the part and the sensor to allow surface digitization of the part surface. This is followed by manual transfer of the scan file onto a post-processing Computer Aided Inspection engineering workstation, where the file is opened in a dimensional comparison and analysis software application. Geometric conformance and deviation are found, and the dimensions indicated in the part computer aided design (CAD) model and/or blueprint are extracted. This information can be reported either in a pass/fail determination report, a partial dimensional inspection report, or a complete dimensional inspection report for subsequent evaluation and part quality determination, as well as manufacturing process optimization.
The Applicant, considered an expert in the industry, has been performing Computer Aided Inspection for 12 years on turbine engine components and medical device components, among many other manufactured parts and products, with the most sophisticated equipment available, mostly based on the use of a tripod-mount or T-mount based 3D Optical Scanner. When operated manually, this 3D surface digitizing system can be used to scan objects of nearly any size. Moving the scanner manually from location to location around the part in order to address all of the part surfaces for visual access and digitizing is a slow and methodical operation. Scanning-processing speed can be increased to a limited extent by use of a 1-axis rotary or 2-axis tilt and rotary tables to move the part in concert with the movement of the scanner.
Other Optical Scanner systems attempt to move the scanner sensor with basic manipulators around the part being scanned. Still other systems have placed the sensor on a traditional pedestal (floor-mounted) robot with the part being scanned on a rotary table. These systems have been plagued with vibration problems and sensor and/or part movement, severely reducing the accuracy and usefulness of the scan data. Gauge Repeatability and Reproducibility (Gauge R&R) studies, as well as inspection results, have shown these problems to be systemic and to result from poor stability of the sensor and part manipulators. Currently the manual operation of a computer aided inspection workstation requires a highly qualified technician to assure proper part placement in relation to the optical scanner.
Typical Optical Scanner output is a point-cloud or polygonized-mesh file that is post-processed either on the scanner computer or, preferably, on a separate workstation computer that does not occupy and consume the scanner computer capacity. Post-processing is the step that generates the typical illustration, analysis, inspection, and report functions of the Computer Aided Inspection process. This is usually performed in two separate sequential steps.
U.S. Pat. No. 7,436,522 to Steinbichler et al., discloses a method to determine the 3D coordinates of the object. The 3D coordinates of a partial surface of the object are determined by a 3D scanner which includes one or more detectors and whose position is determined by a tracking device. The 3D coordinates of an adjacent partial surface of the object are determined by the 3D measuring device. The 3D coordinates of an overlap region of the adjacent partial surfaces are put together by a matching method merging individual scans in a manner so that stacking errors are kept to a minimum.
U.S. Pat. No. 6,917,421 to Wihl, is directed to systems and methods for assessing a dimension of a feature of an object. The system includes an illumination system configured to scan a specimen with light at multiple focal planes substantially simultaneously with multiple collectors. Nearly all light returned from one of the multiple focal planes may be collected by one of the collectors. In addition, the system may include a processor configured to assess dimension of a feature in a direction substantially perpendicular to an upper surface of the specimen using the relative intensity.
U.S. Pat. No. 6,532,064 to Hearn et al., is directed to an automated inspection apparatus for detection of anomalies in a 3D translucent object. The apparatus has a scan head assembly including an image processing unit and image capture device, a first and second light source, and a conveyor. The disclosure is directed to a light block member positioned along a substantially common axis of the image capture device and a light source.
U.S. Published Patent Application Number 2002/0057438 to Decker, is directed to a method and apparatus for acquiring surface topography. The surface topography is acquired by illumination sources with patterns of light from one optical perspective, and the light reflected off the surface is captured by image sensors from an optical perspective that is different than the perspective of the illumination. The images obtained are of the surface with one or more patterns superimposed upon the surface. The surface topography is computed with a processor based upon patterned image data, the known separation between the illumination sources and the imaging sensors, and knowledge about how the patterns of light are projected from the illumination sources.
U.S. Published Patent Application Number 2009/0080036 to Paterson et al., is directed to a scanner system and method that includes a scanner device, a target, and a processor. The scanner device includes an emitter for projecting patterned light and a sensor for capturing images of the object. The target has predetermined features visible to the sensor simultaneously with the object to allow the processor to determine the location of the sensor with respect to the object. This generates a three-dimensional model of the object with the patterned light projected thereon. The scanner further includes light sources for directionally illuminating the object and a sensor is arranged to capture images of the illuminated object. The processor generates sets of photometric data for the object when illuminated from different directions. The processor combines the geometric data and photometric data to output a model comprising geometric information on the object together with photometric information spatially registered with the geometric information.
What is needed, in the art, is a portable system, and also a method of obtaining the accurate and comprehensive dimensional inspection results that are available from 3D scanning with optical metrology and computer aided inspection, while reducing or even removing operator handling to eliminate human induced errors along with the associated lost time to processing steps when a system does not employ seamless and integrated components, especially in a standalone automated system.